Studies Strengthen Links Between Hormones, Women's Cancer

WASHINGTON — Separate studies reported Wednesday by scientists in the United States and Britain strengthen the links between hormone replacement therapy and cancer in older women.

The American study provides further statistical evidence that the therapy, known as HRT, is linked to the incidence of breast cancer.

The British survey provides the first evidence of an association between ovarian cancers and HRT.

Researchers at the M.D. Anderson Cancer Center in Houston said the incidence of breast cancer among Americans leveled off in 2004, following sharp declines in 2002 and 2003.

That provides further evidence of the disease's links to HRT, which also leveled off in 2004 following 18 months of steep declines.

Hormone replacement therapy has been prescribed for years to prevent the discomfort and health problems caused by diminished levels of the hormones estrogen and progesterone following menopause.

However, a highly publicized July 2002 study concluded that risks of hormone replacement outweighed benefits.

HRT usage plunged, from 61 million prescriptions in 2001 to 21 million in 2004. Since then, prescriptions have leveled off.

In women 50 and older, estrogen receptor-positive breast cancers, the kind fueled by estrogen, dropped 14.7 percent in 2002 and 2003, according to the National Cancer Institute.

There was a non-significant decline in breast cancers not related to estrogen.

Many cancer specialists have waited anxiously to see whether the association would continue in 2004, for which breast cancer statistics only recently became available.

In a report to appear Thursday in the New England Journal of Medicine, the M.D. Anderson scientists said the association remains.

The fact that diagnoses of a type of breast cancer called estrogen receptor-positive leveled off in 2004, but did not increase, shows that the previous drop "was not a one-year wonder," said Dr. Peter Ravdin, lead author of the study.

Ravdin cautioned that the studies do not prove a cause-and-effect relationship between use of the medication and breast cancer. But he said they do provide a compelling statistical link.

British scientists will report Thursday in the journal The Lancet that an analysis of health records of nearly 1 million British women show a small but statistically significant link between taking hormone replacements and developing ovarian cancer.

They concluded that between 1991 and 2005, an extra 1,000 women died in the United Kingdom because they were using HRT.

Other factors, such as smoking, use of alcohol, weight and use of oral contraceptives, did not change the statistical results, they said.

California scientists in 1995 discovered a link between cancer of the endometrium, the lining of the uterus, and HRT use.

Cancer specialists say the link between female hormones and cancer is complex. For example, the use of oral contraceptives and breast feeding seem to program the ovaries of young women in ways that protect them from ovarian cancer later in life.

Ravdin said the quick drop in breast cancer diagnoses suggests that withdrawing from HRT may cause small cancers to shrink or even regress.

But he stressed that he does not see his analysis as evidence women should stop using HRT.

In fact, he says he advises his patients to use it — but at the lowest dose and for the shortest time period, in order to control hot flashes and other debilitating symptoms caused by the onset of menopause.